Climate change to undermine world ocean systems by 2100

Washington: Scientists have found that no corner of the world ocean will be untouched by climate change by 2100, with the sea experiencing the simultaneous effects of warming, acidification and oxygen depletion.

In a new study, researchers describe the full chain of events by which ocean biogeochemical changes triggered by human made greenhouse gas emissions may cascade through marine habitats and organisms. Previous analyses have focused mainly on ocean warming and acidification.

Factoring in predictable changes such as the depletion of dissolved oxygen in seawater and a decline in productivity of ocean ecosystems, the new study shows that no corner of the world ocean will be untouched by climate change by 2100. The sea, the world ocean or simply the ocean is the connected body of salty water that covers over 70 percent of the Earth's surface.

By 2100, global averages for the upper layer of the ocean could experience a temperature increase of 1.2 to 2.6 degrees Celsius, a pH decline of 0.15 to 0.31, reductions in dissolved oxygen and diminished phytoplankton production.

"When you look at the world ocean, there are few places that will be free of changes; most will suffer the simultaneous effects of warming, acidification, and reductions in oxygen and productivity," said lead author Camilo Mora, assistant professor at the Department of Geography in the College of Social Sciences at the University of Hawaii at Manoa.

"The consequences of these co-occurring changes are massive - everything from species survival, to abundance, to range size, to body size, to species richness, to ecosystem functioning are affected by changes in ocean biogeochemistry," Mora said.

The human ramifications of these changes are likely to be massive and disruptive. The study shows that some 470 to 870 million of the world's poorest people rely on the ocean for food, jobs, and revenues, and live in countries where ocean goods and services could be compromised by multiple ocean biogeochemical changes.

For the study, researchers assembled global distribution maps of 32 marine habitats and biodiversity hotspots to assess their potential vulnerability to the changes.

Of the many marine habitats analyzed in the study, researchers found that coral reefs, seagrass beds, and shallow soft-bottom benthic habitats would experience the largest absolute changes in ocean biogeochemistry, while deep-sea habitats would experience the smallest changes.